User name R. Feuerbach
Log entry time 15:19:41 on October15,2005
Entry number 156948
Followups:
- 157368 10/19/05 03:30 R. Feuerbach Alignment check
- 157369 10/19/05 03:30 R. Feuerbach Alignment check
Bob and I have decided that the next-iteration (final?) to improve the alignment is to change the momentum settings of the arms to
L-HRS P0 = 3.1234 GeV/c (increase of 3 MeV)
R-HRS P0 = 3.1126 GeV/c (decrease of 5 MeV)
A counting-mode run with the VDCs should be taken tonight to verify these settings.
Below are figures showing events from the Elastic run 2822 compared to the happex detector positions. The tracks have been projected 70cm in Z in the transport system (eg: R.tr.x + .7*R.tr.th, etc.) to get hit locations closer to the detectors.
In each panel, the dispersive axis (X) is vertical, and transverse axis (Y) is horizontal. The top panel in both figures shows the elastic events (black) from run 2822, and events from the -2% runs in red; the -2% runs were 2820 (L-HRS) and 2816 (R-HRS). The lower panel in each figure (blue and green points) show how the elastic events are divided between the two HAPPEX detectors in each arm in run 2822.
In Figure 1, the elastic stripe in the L-HRS is close to the edge of the happex detectors, so we are increasing the momentum (lowering the black-blob) by 3 MeV (shift by 1cm). Since the distribution is not well-centered in Y the splitting of the rate between the detectors is rather poor; this could be fixed by tweaking the septum, however it is not being considered now.
Figure 2 shows a large gap between the edge of the R-HRS HAPPEX detectors, so the momentum of the R-HRS will drop by 5 MeV, which should close the gap by ~2cm. Here the rate is well distributed between the detectors.
FIGURE 1
FIGURE 2
